This invention relates to fire retardant blends comprising olefin polymers and dichlorocarbene-modified butadiene polymers. More particularly, this invention relates to blends comprising polymers selected from the group consisting of styrene polymers and propylene polymers and, as a char-forming flame retardant additive, a dichlorocarbene-modified butadiene polymer.
Dihalocarbene modification of polymers containing ethylenic unsaturation to introduce dihalo cyclopropane units into the polymer chain has long been known. Methods for the preparation of such polymers have been disclosed for example in U.S. Pat. Nos. 3,369,012, 3,676,409 and 3,933,768. The resulting polymers have been shown to be sulfur vulcanizable, to exhibit improved compatability with other rubbers, and to be tough, flame retardant materials. Rubbery butadiene polymers having from 5 to 20 percent of the ethylenic unsaturation dibromo carbene-modified were also disclosed as a useful polymeric flame retardant rubbery substrate for the preparation of high impact polystyrene compositions in U.S. Pat. No. 3,639,522.
The use of organo-halogen compounds as flame retardant additives for polymers is widely practiced. Many are employed together with a synergist such as antimony oxide to improve flame retardant behavior, and the use of polymeric halogen compounds such as polyvinylchloride in blends with other polymers to impart flame resistance is also widely practiced. In as much as polymers vary widely in their burning behavior, whether particular organohalogen compounds or halogen containing polymers will effectively reduce the flammability of a specific plastic material cannot be readily predicted.